High voltage switch contact surface



April 16, 1963 L. NAGEL HIGH VOLTAGE swI'rcH coN'rAc'r SURFACE Filed Sept. 28, 1960 I l J & my 2 WN W 0 2 mm 5 L. .w v. 2 B

United States Patent 3,086,099 HIGH VOLTAGE SWITCH CONTACT SURFACE Lester L. Nagel, Summit, N.J., assignor to Buell Enginearing Company, Inc., New York, N.Y., a corporation of New York Filed Sept. 28, 1960, Ser. No. 58,952 8 Claims. (Cl. 200-464) This invention relates to electric switches for high voltage capacitive circuits. More particularly, it relates to electric switch contacts particularly useful in immersed switches for controlling electric precipitating equipment; but the invention is not limited to such use. Such equipment in some applications is rated for 93 kv. and 0.5 ampere peak load.

In designing equipment for such high voltage use, it is important that there be high contact pressure over as large an area as practical. Although point-contact at one point will give high pressure, the area is likely to be so limited that arcing or corona discharge may take place around the point of contact. It is important that the contact pressure be great so as to break the oil film between the surface of the fixed and movable contact elements and thus avoid an underdesirable switch capacitance effect which interferes with proper functioning of the equipment being controlled.

It is desirable also that the movable contact be insertable readily into and removable from engagement with the fixed contact and that the movable contact be able to pass through the fixed contact in moving onto a new connection.

Therefore, it is an object of the invention to provide an improved contact structure for high voltage capacitive circuit electric switches having provision for applying concentrated pressure between the fixed contact surface and movable contact element over a greater area than alforded by point-contact.

Another object is to provide an improved contact structure of the above type in which the fixed contact surface is resiliently adjustable to the movable contact element.

Another object is to provide an improved contact structure of the above type in which the movable contact may pass through the fixed contact in going onto a new connection.

Another object is to provide an improved contact structure of the above type which can be economically manufactured, assembled and serviced.

Other objects and advantages will appear as the invention is described in connection with the accompanying drawing.

In the drawing:

FIG. 1 is an isometric side elevation view of a high voltage switch embodying the invention.

FIG. 2 is an end detail view, partly in section, of the fixed contact structure.

FIG. 3 is a section view taken along line 33 of FIG. 2.

FIG. 4 is a fragmentary perspective view of the fixed contact with movable contact element in engagement therewith.

FIG. 5 is a fragmentary detail view in end elevation similar to FIG. 2 of another form of fixed contact structure.

Referring to the drawing, the switch frame may conveniently consist of two spaced circular insulating plates and 12 connected by six spaced contact supporting bars 1449, inclusive, equally spaced around the peripheries of the top and bottom insulating plates and with the bars parallel to the axis of the switch and attached at their tops and bottoms to the plates 10 and 12.

One or more fixed contact members, designated generally by the numeral 20, may be mounted rigidly upon the inside surfaces of the connecting bars 14-19 by screws or other suitable means. Usually there are three such fixed contacts on each bar, one above the other, so that the positions of the fixed contacts on one bar will be diametrically opposite the fixed contacts on a diametrically opposite bar on the opposite side of the switch structure (for example the bars 14 and 17). This is in order that fixed contacts on the various bars and at various levels in diametrically opposite positions will be engaged and disengaged successively by one arm or the other of a bridging contact member, designated generally by the numeral 30, as that element is rotated.

Each bridging contact consists preferably of a pair of radially extending rods 31 and 32 diametrically oppositely located with respect to a central mounting member 33 which is mounted on an operating spindle 36. This spindle is mounted coaxially with respect to the top and bottom plates 10 and 12 for rotativc movement by any desired or suitable lever, handle or other operating means.

The inner ends of rods 31, 32 may be screwthreaded for mounting in tapped axial endwise bores in the oppositely extending arms of mounting member 33.

Each fixed contact 20 comprises a block of generally rectangular shape with a channel or passageway 22 formed therein extending lengthwise of the block in position for the end portions of the movable contact elements 31, 32 to enter and pass through as the movable contact member is rotated.

Within the channel 22 and cut or otherwise suitably formed in the upper wall or ceiling thereof near the ends of the channel are two oppositely and upwardly inclined narrow slots 24, 26 to receive the upwardly and outwardly inclined ends 28a, 28b of a U-shaped contacting element 28, preferably made from a strip of resilient spring metal of high conductivity such for example as Phosphor bronze.

The contacting element 28 is preferably flat and straight in its central portion so as to be able to make a line contact with and exert great pressure upon the upper surface of the end of the movable contact rods 31, 32. Preferably, the movable contact rods will be inclined at a slight angle of approximately 1 or 2 to the horizontal as will the floor or bottom surface of the channel. The flexible contacting element 28 will be able to accommodate itself to the movable contact elements 31, 32 due to the inherent resilience of the flexible contact.

The channel 22 is greater in height than the diameter of the contact rods 31, 32 to provide room for the re silient element 28 and for the contact rod, which must be able toenter the channel and engage the resilient element 28 at the top and solid wall of the channel at the bottom.

Preferably the flexible element 28 of the fixed contact is assembled in the fixed contact block 20 by flexing and inserting the ends 28a, 28b into the slots 24, 26. The flexible element is then released and its tips are welded into the slots.

An alternative form of means of securing the flexible element to the fixed contact block is illustrated in FIG. 5. In this form, the flexible element 40 is of generally U- shape with outturned ends (see 41 for example) which lie flat against the ceiling or top surface of the channel 42 and are spot-welded thereto adjacent the ends of the channel. In other respects, the flexible element 40 is similar to the flexible element 28 previously described and functions in the same way as the element 28.

From the foregoing, it will be apparent that both forms of the fixed contact structure illustrated and described provide for great contact pressure between the movable contact elements 31, 32 and the fixed contact structure. The pressure of the flexible element of the fixed contact is along a line where it engages the top of the curved surface of the rods 31, 32 along a line where they engage the solid bottom wall of the channel. The structure, thus, provides for great pressure over an area greater than a point-contact and doubles the area because of both top and bottom engagement.

In old styles of blade contacts, there was too great a surface for as much pressure to be exerted between the movable contact element and the fixed contact surface as can be exerted in the present invention, it being a well known physical fact that when a given pressure is exerted between two elements, the pressure per square inch is in inverse proportion to the area over which the pressure is exerted. Thus, the present invention affords a considerable improvement over high voltage switch contact structures as heretofore known, both of the point-contact type and the blade type. It avoids the resistive-capacitance effect which heretofore was detrimental due to insufiicient breaking of the oil film, and avoids the corona effect which was quite common in connection with contact structures providing point-contact between spherical surfaces or between a spherical surface and a flat surface.

Many modifications within the scope of the invention will occur to those skilled in the art. Therefore, the invention is not limited to the exact forms illustrated and described.

What is claimed is:

1. In an electric switch for high voltage capacitance circuits, movable contact means mounted for rotation about an axis and having a radially extending end portion, fixed contact means comprising a member presenting an uninterrupted fiat face substantially parallel with respect to the plane of rotation of the end portion of said movable means, electrically conductive contacting means secured to said member presenting an uninterrupted flat face substantially parallel to said first face, the end portion of said movable contact means passing between said faces as said movable contact means rotates. said radially extending portion making a line contact with said can tacting means along an uninterrupted straight line when the movable contact is at rest, and means pressing said movable and said fixed contact means togethcr and concentrating pressure along said line.

2. The combination as claimed in claim 1 wherein the contacting means is generally U-shaped with its ends attached to said fixed member.

3. The combination as claimed in claim 1 wherein the contacting means comprises a flexible resilient strip.

4. The combination as claimed in claim 3 wherein the strip is U-shapcd with its ends inserted in slots formed in said fixed member.

5. The combination as claimed in claim 1 wherein said radially extending portion is cylindrical.

6. In an electric switch, fixed contact means, movable contact means mounted for rotation about an axis and for engagement with and separation from said fixed contact means, said fixed contact means having a contacting portion presenting an uninterrupted flat face, said movable contact means having a radially extending end portion adapted to make line contact with said fiat face along an uninterrupted straight line when said movable contact means is at rest, and means pressing said movable and said fixed contact means together and concentrating contact pressure along said line.

7. The combination as claimed in claim 6 wherein said uninterrupted face is on a flexible contact member which is a generally U-shaped strip having its ends attached to said fixed contact means.

8. The combination as claimed in claim 6 wherein said radial extension is cylindrical and said fiat face is substantially parallel with respect to the plane of rotation of the end portion of said movable contact means.

Reid Dec. 30, 1902 Catalano et al June 11, 1957 

1. IN AN ELECTRIC SWITCH FOR HIGH VOLTAGE CAPACITANCE CIRCUITS, MOVABLE CONTACT MEANS MOUNTED FOR ROTATION ABOUT AN AXIS AND HAVING A RADIALLY EXTENDING END PORTION, FIXED CONTACT MEANS COMPRISING A MEMBER PRESENTING AN UNITERRUPTED FLAT FACE SUBSTANTIALLY PARALLEL WITH RESPECT TO THE PLANE OF ROTATION OF THE END PORTION OF SAID MOVABLE MEANS, ELECTRICALLY CONDUCTIVE CONTACTING MEANS SECURED TO SAID MEMBER PRESENTING AN UNINTERRUPTED FLAT FACE SUBSTANTIALLY PARALLEL TO SAID FIRST FACE, THE END PORTION OF SAID MOVABLE CONTACT MEANS PASSING BETWEEN SAID FACES AS SAID MOVABLE CONTACT MEANS ROTATES, SAID RADIALLY EXTENDING PORTION MAKING A LINE CONTACT WITH SAID CONTACTING MEANS ALONG AN UNINTERRUPTED STRAIGHT LINE WHEN THE MOVABLE CONTACT IS AT REST, AND MEANS PRESSING SAID MOVABLE AND SAID FIXED CONTACT MEANS TOGETHER AND CONCENTRATING PRESSURE ALONG SAID LINE. 